Experimental Investigation of Rice Husk Spontaneous Ignition

The experimental study of spontaneous ignition of rice husk was carried out with the following objectives: (1) to determine the self-ignition temperature of rice husk using the Frank-Kamenetskii method, (2) to find the kinetic parameter of rice husk spontaneous ignition, and (3) to determine the safe storage size of rice husk piles to prevent spontaneous ignition. The experiment was conducted using rice husk with an initial moisture content of 11% (wet basis) and a bulk density of 223 kg/m³, which was placed in rectangular cubic-shaped test cages of three different sizes, namely, 8³, 10³, and 12³ cubic centimeters, with a gap size of 0.5 mm. The experiment was conducted in an oven with good air circulation. The results of the study revealed that (1) the self-ignition temperature of rice husk was 188 °C, 181 °C, and 175 °C for the rectangular cubic-shaped cages with dimensions of 8³, 10³, and 12³ cubic centimeters, respectively, (2) the kinetic parameter of rice husk spontaneous ignition in term of activation energy () was found to be 114.7 kJ/mol, and (3) the safe storage size of rice husk piles was determined to be the area below the graph at ambient temperature of 40 °C. For a cylindrical-shaped pile of rice husk with a radius () of 40 meters and a height () not exceeding 30 meters, and for a rectangular-shaped pile with a height () not exceeding 60 meters and a length () less than 40 meters and depth () not exceeding 10 meters (with a length () -to-depth () ratio of 4).